In recent years two trends, global warming and personal mobility, have come together to create a demand to reduce wasted electrical power. Global warming concerns have attracted public and government attention, prompting increased interest in reducing wasted electrical power consumption where possible. Advances in electronics, communications, and the internet have resulted in electrical devices that enable people to do many tasks also at home, in libraries and at other locations that were typically done only in an office. In addition, advances in battery technology have resulted in more versatile portable electronic devices that have enabled people to perform traditional office functions at more desirable and varied locations outside of an office or home. Moreover, external electrical power adapters have become more common as a means to convert electrical power from common electrical outlets into various forms used by these electrical devices and a means to power electrical devices in various locations.
Standby power is power consumed by electrical devices when a device is not in use but still connected to a source of power and is often considered wasted power. One form of wasted electrical power is the electrical power consumed by external electrical power adapters when attached electrical devices no longer need to consume electrical power or are disconnected from the power adapters. Although the electrical devices are not consuming power for an intended task, power is still consumed when electrical devices are attached to the power adapters and the latter are attached to power sources. Also the adapter still consumes power even after the device is disconnected from the adapter.
External power adapters have been modified to reduce wasted power consumption in these situations. Several power adapters have been disclosed that use monitoring circuitry to reduce current coming from a source of power into the power adapters when the electrical device is not in use, when the device is turned off or when the device is disconnected. Some use monitoring circuits and rechargeable batteries placed in devices to turn off a power adapter that they are connected to when not in use. However, all of these adapters may consume some power when devices are removed and adapters are left attached to power sources. Also, the monitoring circuitry itself consumes power when the device is attached to the adapter and consuming power. In adapters that use non-rechargeable batteries, the power adapter becomes inoperable with time.
There is still a need for an external electrical power adapter electrically attached to a source of power that does not draw any power from any source of electrical power when the adapter is physically disconnected from an electrical device that consumes electrical power.